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            <h2 class="title" style="clear: both"><a id="timesync"></a>Time Synchronization</h2>
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      <p>
            For best results, you should synchronize the clocks used by all
            machines in a replication group. If you are using a time-based
            consistency policy, this is an absolute requirement
            (see <a class="xref" href="consistency.html#timeconsistency" title="Time Consistency Policies">Time Consistency Policies</a> for more information).
            Time synchronization is easily achieved using a mechanism like <a class="ulink" href="http://www.ntp.org/" target="_top">NTPD</a>.
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      <p>
            In addition, time synchronization is also a requirement for
            internal JE HA bookkeeping.  For example, JE checks for clock
            skew between the Master and a Replica
            when the Replica performs its startup handshake with the
            Master. This handshake will abort and throw
            <a class="ulink" href="../java/com/sleepycat/je/EnvironmentFailureException.html" target="_top">EnvironmentFailureException</a> if the clock skew between the
            two machines is greater than the value set for the
            <a class="ulink" href="../java/com/sleepycat/je/rep/ReplicationConfig.html#MAX_CLOCK_DELTA" target="_top">MAX_CLOCK_DELTA</a> property. This property can be set using the
            <a class="ulink" href="../java/com/sleepycat/je/rep/ReplicationConfig.html#setMaxClockDelta(long, java.util.concurrent.TimeUnit)" target="_top">ReplicationConfig.setMaxClockDelta()</a> method, or in the JE
            configuration file using the
            <code class="literal">je.rep.maxClockDelta</code> property.
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            Finally, well synchronized clocks make it easier to correlate
            events in the logging output from different nodes in the group.
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